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1. Field of the Invention
The present invention relates to an apparatus for installing pipe in a wellbore, such as an oil or gas well. More particularly, this invention relates to an apparatus for determining when movable elevators in a drilling rig are properly positioned relative to a section of pipe to be installed in a wellbore. More particularly still, this invention relates to an apparatus which can provide a signal when elevators, and more specifically the slips of such elevators, are positioned at a desired location relative to a section of pipe to be installed in a wellbore and, conversely, when such elevators and slips are not so positioned. More particularly still, the present invention relates to an apparatus which can be used to prevent elevator slips from being closed when such elevator slips are improperly positioned relative to a section of pipe to be installed in a wellbore.
2. Description of the Related Art
Standard rotary drilling rigs are typically comprised of a supportive rig floor, a derrick extending vertically above said rig floor, and a traveling block which can be raised and lowered within said derrick. During drilling operations, such rig equipment is often used to insert and, in some cases remove, tubular goods from a well situated under such derrick. For example, drill bits and/or other equipment are often lowered into a well and manipulated within such well via tubular drill pipe. Moreover, once a well has been drilled to a desired depth, large diameter pipe called casing is often installed in the wellbore and cemented in place in order to provide structural integrity to the well and to isolate downhole formations from one another.
When installing casing, drill pipe or other pipe into a well, such pipe is typically installed in a number of sections of roughly equal length. These pipe sections, often called xe2x80x9cjoints,xe2x80x9d are typically installed one at a time, and screwed together or otherwise joined end-to-end to make a roughly continuous length of pipe. In order to start the process of inserting pipe in a well, a first joint of pipe is lowered into the wellbore at the rig floor, and suspended in place using a set of xe2x80x9clower slips.xe2x80x9d Such lower slips are often wedge-shaped dies which can be inserted between the outer surface of said pipe and the bowl-like inner profile of the rotary table. Such lower slips hold the weight of the pipe and suspend the pipe in the well. Although such lower slips can be automated, in many applications such lower slips are manually inserted and removed by rig personnel.
During the process of installing pipe into a well, a first joint of pipe is generally inserted into a well and positioned so that the top of said joint of pipe is located a few feet above the rig floor. A rig crew or a pipe handling machine grabs a second joint of pipe, lifts said second joint of pipe vertically into the derrick, positions said second joint above the first joint which was previously run into the well, and xe2x80x9cstabsxe2x80x9d a male or xe2x80x9cpin-endxe2x80x9d thread at the bottom of said second joint into a female or xe2x80x9cbox-endxe2x80x9d thread at the top of the first joint. The second joint is then rotated in order to mate the threaded connections of the two joints together.
Thereafter, a set of elevators attached to the traveling block in the rig derrick is typically lowered over the top of the second (i.e., upper) joint of pipe. Such elevators have a central bore which is aligned with the uppermost end of the joint of pipe. The pipe is received within the central bore of the elevators. Once the elevators have been lowered over the pipe a desired distance, slips within such elevators can be activated to latch or grip around the outer surface of said joint pipe. Depending on the length of the second joint of pipe, this can often occur 40 feet or more above the rig floor.
Once the elevator slips are properly latched and engaged around the body of the pipe, the traveling block and elevators can be raised to take weight off of the lower slips. The lower slips can then be removed. Once the lower slips are removed, the entire weight of the pipe string is suspended from the elevator slips. The pipe can then be lowered into the well by lowering the traveling block. After the second or upper joint of pipe is lowered a sufficient distance into the well, the lower slips are again inserted in place near the rig floor. The process is repeated until the desired length of pipe (i.e., the desired number of joints of pipe) is inserted into the wellbore. This same process is typically utilized for many different types and sizes of pipe whether small diameter drill pipe or large diameter casing.
At certain points during this process, the entire weight of the pipe is being held or suspended by the elevators and, more specifically, the elevator slips. This pipe can be very heavy, especially when many joints of large diameter and/or heavy-wall casing are being run into a well. Accordingly, it is extremely important that the elevator slips must be properly latched around the uppermost section of pipe in the derrick to ensure that such pipe remains securely positioned within said elevators. If the pipe is not properly secured within such elevators, it is possible that the pipe could drop or fall out of the elevators, thereby causing damage to the rig or the well, or injury to rig personnel.
In many cases, a female or box-end threaded connection of a joint of pipe includes an xe2x80x9cupset,xe2x80x9d whereby said connection has a larger outer diameter than the rest of the pipe body. In other instances, pipe joints are joined together using internally threaded couplings; such couplings also have a larger outer diameter than the remainder of the pipe body. In either case, care must be taken to ensure that elevator slips, which are designed to engage against the outer surface of a pipe body (as opposed to the coupling or connection upset), are indeed aligned with said pipe body. If such elevator slips are inadvertently closed against a coupling or connection upset, such slips likely will not fully contact or engage against the outer surface of the pipe. This is true even when such slips are partially aligned with a connection upset or coupling. As a result, slips (including elevator slips) which are not properly engaged against a pipe body may not grip such pipe securely. If the slips do not grip the pipe securely, such slips may not be able to support the weight of the pipe string, and the pipe can fall out of the slips.
In one common method of installing or running casing into a wellbore, a worker is stationed on a platform in the derrick at approximately the height where elevator slips are closed on the top of a section of pipe, which can often be approximately forty (40xe2x80x2) feet or more above the rig floor. The worker, often referred to as a xe2x80x9cderrick man,xe2x80x9d visually observes when the elevators have been properly lowered over the top of a section of pipe and positioned relative to said section of pipe. The driller, who is located on the drill floor, controls the vertical positioning of the traveling block and the elevators attached thereto. Once the derrick man observes that the elevators are properly positioned relative to the body of the section of pipe (that is, that the elevator slips are not positioned adjacent to a connection upset or external coupling) the derrick man typically uses shouts or hand signals to communicate this fact to the driller. The elevator slips are then latched around the body of the pipe. Thereafter, the driller can pick up on the traveling block thereby lifting the entire weight of the pipe. In some cases, this positioning of the elevators relative to the uppermost section of pipe is determined or confirmed using one or more closed-circuit video cameras mounted in the derrick which can provide a video image of such elevators to personnel located on the rig floor or at other locations on the rig.
It is often very difficult for a driller or other operator situated on the rig floor to determine whether elevators are properly positioned relative to the top of a joint of pipe suspended in the derrick without some assistance from a derrick man or other device. First, a distance of 40xe2x80x2 or more typically separates the rig floor from the top of the pipe joint where the elevators must be latched. Second, in many instances, the driller""s perspective makes such task difficult because he must look virtually straight up to see the position of elevators. As a result, it is frequently difficult for someone standing at the rig floor to judge the actual position of the elevators relative to the pipe joint.
Furthermore, it is also often difficult for a derrick man to judge when elevators are properly positioned relative to a joint of pipe suspended in a derrick. Even though the derrick man may be positioned on an elevated platform in the derrick, he still may not be close enough to the top of the pipe to accurately determine when the elevators have cleared the connection upset or external coupling. Moreover, even if the derrick man can see when the elevators are properly positioned on said joint of pipe, there is always a risk of miscommunication between the derrick man and the driller, especially when shouts or hand signals are used.
Accordingly, it is an object of the present invention to provide a means for determining when elevators, and more particularly the slips of such elevators, are positioned in a desired location relative to the top of a section of pipe to be gripped by said elevators. Further, it is an object of the present invention to provide a means for signaling to a driller and/or other rig personnel when such elevator slips are properly positioned relative to a section of pipe to be gripped by said elevators. Likewise, it is an object of this invention to provide a means for signaling to a driller and/or other rig personnel when elevator slips have passed over a connection upset or external coupling, such that said slips are located adjacent to the body of a section of pipe and, therefore, in a proper position to grip or fully engage against such pipe.
The present invention relates to a device which can determine when a set of elevators is properly positioned relative to a section of pipe to be gripped by the slips of such elevators. The present invention uses one or more sensors to determine when a set of elevators, and more particularly the slips of such elevators, are properly positioned relative to a section of pipe suspended in a derrick. In the preferred embodiment of the present invention, such sensors are optical sensors, such as an electric eye, mounted at or near the top of such elevators. Such optical sensors are mounted a predetermined distance above the upper surface of the elevators. The optical sensors are used to determine whether such elevators are properly positioned near the top of the pipe to be gripped by the elevator slips.
Generally, elevators have a central bore extending through the body of said elevators. When such elevators are lowered around a joint of pipe to be latched, the pipe itself is received within said central bore of the elevators. As the pipe passes through the central bore of such elevators, it eventually protrudes through the upper opening of said central bore near the upper surface of the elevators.
In the preferred embodiment of the present invention, one or more optical sensors are situated on the upper surface of the elevators near the upper opening of the central bore of the elevators. The sensors emit a beam of light or other optical signal which crosses the upper opening of said central bore. As the elevators are lowered along the length of the pipe, the top of the pipe eventually protrudes through the upper opening of the central bore and breaks the optical signal emitted between the optical sensors. Put another way, the optical sensors recognize when the elevators have progressed far enough down the length of a joint of pipe to ensure that said elevators are not positioned adjacent to a connection upset or coupling. Once said elevators are properly positioned, the elevator slips can be latched to fully grip and engage against the body of the pipe.
When the signal emitted by the optical sensors is broken, a signal (sound and/or visual) is sent to the driller or other operator at the rig floor, thereby indicating that the elevator slips have cleared the connection upset and/or coupling, and that the elevators are in the desired position. The elevator slips can then be actuated to close against the pipe body and grip said pipe. The system can also be automated to prevent the elevator slips from latching unless the appropriate signal is received from the sensing means mounted above the elevators.